Nitrous oxide (NO2) can be a finicky power adder for your engine. It is composed of two oxygen molecules for every one nitrogen molecule. This mixture is not a fuel and doesn't produce power by itself, but it gives you the ability to burn more fuel to create more power-think of it as a catalyst. If used improperly, it has the potential to blow engine parts through your truck's hood. However, when used correctly with the sufficient components, nitrous oxide will without a doubt provide the most amount of power for the least amount of money. It can be used on nearly any engine without severely degrading the life of the engine. Generally, nitrous is considered a mod that only gets plumbed into little tuner cars or large V-8s that displace lots of cubic inches and have a quarter mile to go. But with so many guys trading in their V-8s for four and-six-cylinder ORVs, it was time to see what a bottle of NO2 could do to a mild Jeep I-6. We didn't want a kit that would break our bank, nor did we want one without any safety parameters that would stop the nitrous flow if the fuel flow stops. It sounded like a stretch, but after talking to Zex we were confident it could be accomplished with its 4 &-6-Cylinder Nitrous System for EFI engines.There are various delivery methods to get the nitrous in the engine, but they are mainly distinguished as either a "dry" or "wet" kit. In an EFI-equipped engine, a dry system injects only nitrous into the intake. It then relies upon tricking the factory ECU into dumping more fuel into the engine to mix with added nitrous oxide. Dry systems can only add small amounts of horsepower (around 60 hp) because they utilize stock injectors to dump more fuel. A wet system actually plumbs into your existing fuel lines and not only dumps nitrous oxide into the engine, but also extra fuel (usually combining the two at a single nozzle) just upstream of the throttle body. Much more power can be safely added to an engine with a wet system, but a good rule of thumb is to never add a nitrous shot that produces more than 33 percent of the engine's [pre-nitrous] power. With 100,000 miles on our stock inline 6's fuel injectors and engine sensors, we decided to go with a Zex wet system that would provide a 55 to 75 hp shot of nitrous. We also obtained the Blackout edition of the kit that uses black fuel and nitrous lines, a black control box, and a black nitrous bottle. We figured it made sense to keep the nitrous kit as hidden as possible.
The ZEX wet system uses a Nitrous Management Unit which controls the entire nitrous system, has built-in safety systems, and makes for a simple two-hour installation. This pre-assembled unit uses features such as Zex's patented Active Fuel Control to monitor the bottle pressure and regulate the amount of fuel added to the mixture. This ensures that the engine is never run too rich or too lean. The Zex kit also utilizes a simple and intelligent activation method: the Nitrous Management Unit (NMU) learns the voltage curve of the vehicle's throttle position sensor (TPS) and when powered, will activate injection at wide open throttle (WOT). The fuel and NO2 is the fed to the Zex nitrous nozzle where it is mixed and then finely atomized during injection by the nozzle's patent pending Fuel Shear technology. This kit is adjustable between a 55 hp and 75 hp shot of nitrous with the use brass nozzles of varying diameter to limit the amount of nitrous available.
 The simplicity of this kit...  The simplicity of this kit allowed us to hook it up one night after work. Since this kit only requires simple modifications to be made, we would have been able to stop the installation in the middle and still drive to work the next morning. Remember that it is NOT legal to have the nitrous bottle attached on the highway! We wanted the kit hidden from sight (thus the Blackout option), but after some test fitting we had to move it to a less confined space. |  This is the NMU control box...  This is the NMU control box that manages the fuel and nitrous flow. The "Out" ports (on the other side of the unit) are clearly labeled for fuel and nitrous. The "In" ports use larger fittings to ensure there is always enough supply to meet the regulated demand, and so you don't hook up the kit backwards. This all-inclusive control box greatly simplifies the installation of the kit and has built-in safety features to keep your engine alive. |  Sometimes a wet kit requires...  Sometimes a wet kit requires you to splice or "T" into the fuel lines. One of the nicest features of this kit was that the fuel supply line tied right into the nipple on the fuel rail. The main issue with wet kits is making sure that the fuel pump can supply enough fuel to both the injectors and the NMU. However, if the unit isn't getting enough fuel, it will restrict the supplied amount of nitrous to ensure that the engine never runs lean. |
 After some test fitting in...  After some test fitting in a tight Cherokee engine compartment, we decided that the best spot for the NMU would be stuck to the side of the air intake box. We found a spot in the corner of the firewall next to the fender, but we decided that would be a bad point of impact during a crash and not somewhere you'd want to mount a control box with fuel lines and nitrous running through it. Mounting to the side of the air intake box was not ideal, but it would be a safe place to have the NMU mounted in the event of an accident. We used adhesive tape and bolts with nuts to secure it. |  Two stainless braided and...  Two stainless braided and insulated high pressure lines feed nitrous and fuel from the NMU control box to a single Zex injector...... |  ......That injector is threaded...  ......That injector is threaded into a bung that mounts on the air intake tube. When the control box receives a signal from the TPS sensor that indicates WOT,..... |
 .......the NMU allows both...  .......the NMU allows both nitrous and excess fuel to flow to the single Zex nozzle and atomize in the air intake stream just before the throttle body........ |  ......The cold, condensed...  ......The cold, condensed oxygen combined with the extra fuel will generate around 70 more horsepower in this engine-roughly 30 percent of the engine's available output before the nitrous (within standard safe range). |  There are three wires that...  There are three wires that come off the NMU control box, making installation quick and painless. The black wire runs to a negative ground, while the red wire runs to the on/off switch that you need to mount inside your vehicle somewhere....... |
 .......We found a spot for...  .......We found a spot for our switch in a blank hole on the dash near a couple factory switches. The toggle switch should have power routed through it from a switched ignition lead that will only be "on" when the vehicle is running. |  The position that you mount...  The position that you mount the tank at is very important. The pickup of most systems (unless ordering a special bottle to be run upside down) is in the very bottom of the tank, and is a fixed tube. Therefore, it's important to mount the tank with this tube at the lowest point so it can pick up the heavier nitrous oxide gas in the bottom of the tank. It's also important to mount the tank with the valve pointing towards the front of the vehicle so the nitrous is driven towards the bottom of the bottle when accelerating. One thing to note is that, even though these were high-quality bottle brackets, we would have been much more pleased with them had they set the bottle at more of an angle (like most nitrous bottle brackets we've seen). Having the bottle lay almost flat like this makes it imperative to properly mount it with the valve handle pointing forward. | |